It is well-known that the illusion of three-dimensional or stereoscopic images can be created by providing a separate image to each eye of the observer with each image representing a point of view from a different viewing angle. For example, a pair of cameras can be arranged to photograph an object at two slightly different viewing angles, and if each view is provided separately to each eye of the observer, the observer will perceive that object as stereoscopic or three-dimensional (3-D).
Using this principle, many different systems have been devised over the years to provide a stereoscopic or 3-D illusion. One such stereoscopic system which has been used primarily in movie theaters, and to some extent more recently in television, is a system in which the observer must wear specially designed viewing glasses in order to perceive the stereoscopic image or images. These viewing glasses typically include a pair of monochrome color filters as lenses, for example red and blue filters, which separate or filter multi-colored composite images into distinct right-left image pairs which are separately provided to the right and left eye of the viewer. A similar stereoscopic system uses viewing glasses that are provided with light polarizing filters rather than color filters that act to separate or polarize a composite, multi-polarized picture into discrete right-left pictures of different polarities to provide a distinct picture to each eye of the observer.
Even more complicated systems employ liquid crystal shutters incorporated into viewing glasses or goggles whereby image pairs are alternately displayed to each eye to create the stereoscopic effect. In such systems, the right and left views are displayed through a voltage controlled liquid crystal shutter provided for each lens of the glasses or goggles and are displayed at very short time intervals such that when one image is directed to one eye, the image directed toward the other eye is darkened by the liquid crystal shutter.
Other stereoscopic systems use lenticular screens or frames which consist of a plurality of adjacent, vertically arranged lenticular lenses. These lenticular lenses or screens have been widely used with two-dimensional still pictures such as with postcards and other novelty items to display a stereoscopic image when viewed from proper viewing angles. The stereoscopic effect is generated by positioning each lenticular lens over a discrete vertical column of picture elements or pixels. The lenticular lenses are appropriately curved or provided with a prismatic surface to direct a distinct image to each eye to create the 3-D or stereoscopic effect.
Such lenticular screens have also been used in connection with moving pictures such as with television, for displaying stereoscopic motion pictures by optically isolating picture elements or pixels of a television screen in the horizontal domain to allow independent viewing by each eye creating the stereoscopic effect. In one arrangement, a lenticular screen is affixed to the outside of a picture tube. Another approach is to provide the lenticular screen within the picture tube.
In recent times, however, there has been increasing interest in providing 3-D or stereoscopic display devices with the rise of electronic arcade games, personal computers and hand-held video games. There has also been a recent proliferation of 3-D or "player point-of-view" video games which attempt to create a three-dimensional or walk-around effect by providing scenes in the game from the player's point of view or vantage point where the video screen stimulates the player's actual field of vision. In this manner, the view that the player sees on the screen changes as the player looks to the right or left, for example, and likewise as the player moves from one location to another. In addition, the number of video games and other applications that employ so-called "virtual reality" technology, in which there is a simulated walk-around or 3-D effect, has also dramatically increased.
Although there is an increased demand for 3-D or stereoscopic display devices, the stereoscopic systems currently available nevertheless have many drawbacks. For example, systems that use color or polarizing filters require special glasses having frames that are typically made from cardboard and are mass-produced as one-size-fits-all. These glasses are usually uncomfortable and awkward to wear, and have been known to cause headaches when worn for long periods of time. Liquid crystal shutter goggle systems also suffer from these same problems and, moreover, are expensive and quite heavy to wear due to the liquid crystal shutters and accompanying electronics. These shutter systems can also severely restrict and even eliminate the observer's field of vision of the surrounding environment when the goggles are being worn.
By contrast, systems that employ lenticular screens substantially eliminate the problems associated with the use of special glasses or goggles. These lenticular screen systems, however, tend to be more difficult to use with moving image display devices such as television or hand-held electronic games. One problem with these lenticular screen systems arises from the fact that many hand-held televisions and nearly all hand-held video games today use liquid crystal displays (LCDs). These LCDs are desirable because they eliminate the need for a large picture tube and thus can provide very flat viewing screens and light-weight portable display devices. However, a significant problem with LCDs is that they can only be seen clearly from limited viewing angles because of the light collimating property of the liquid crystals. Thus, as a typical LCD is observed from wider viewing angles, less light passes through the crystals to the observer and thus the viewing screen darkens. Accordingly, typical LCDs are less than ideal for use with a lenticular screen since it is desirable to provide a wider viewing angle for a more realistic walk-around or three-dimensional effect.
Attempts have been made incorporating stereoscopic display devices with LCDs. For instance, U.S. Pat. No. 4,953,959 to Dallas discloses that stereoscopic images can formed in accordance with one aspect of the invention which provides a device for forming images comprising a pair of spaced constituent pictures formed by a LCD which are arranged one behind the other. To create the 3-D images, a pair of polarizers or LCD devices are employed such that the resulting picture viewed by the observer is dependent on the sum of the rotations of the plane of the polarization of the light passing through the constituent pictures as well as on the polarization direction of the two polarizers relative to one another.
Other stereoscopic LCD display systems employ lenticular screens or frames to generate 3-D images. For example, in U.S. Pat. No. 4,584,604 to Guichard et al., a matrix of liquid crystal cells is provided and appropriately spaced behind a lenticular frame or screen to thereby form a three-dimensional image. The center of each matrix element is displaced with respect to the center of each lenticular lens. Likewise, U.S. Pat. No. 4,945,407 to Winnek discloses a high-definition three-dimensional television that uses a lenticular screen placed over an imaging plane consisting of an active matrix LCD panel. U.S. Pat. No. 4,959,641 to Bass et al. provides a stereoscopic display device that uses a plurality of independently controlled and discrete light sources such as a liquid crystal array provided in a fixed relation to a lenticular screen. None of these stereoscopic LCD devices, however, satisfactorily address the problems associated with the undesired collimating effect of the liquid crystal material which provides only a narrow viewing field directly in front of the display device, and hence a less realistic 3-D or walk-around effect.
Accordingly, there is a need to provide an improved stereoscopic display system that eliminates the need for special glasses or goggles. Moreover, there is also a need to provide such a system that is capable of displaying improved stereoscopic images when used with LCDs to achieve clearer and improved 3-D images and wider viewing angles, and more realistic walk around effect. The present invention addresses these and other needs.